Magnetic write head with dual return pole

ABSTRACT

Disclosed herein are magnetic write heads and data storage devices comprising such write heads. A magnetic write head comprises a leading side, a trailing side, an air-bearing surface (ABS), a main pole disposed between the leading side and the trailing side and extending to the ABS, a first return pole disposed between the main pole and the leading side, and a second return pole disposed between the main pole and the trailing side. One or both of the main pole and the second return pole may be tapered.

BACKGROUND

Higher storage bit densities in magnetic media used in disk drives havereduced the size (volume) of data cells to the point where the celldimensions are limited by the grain size of the magnetic material.Although grain size can be reduced further, the data stored within thecells may not be thermally stable. That is, random thermal fluctuationsat ambient temperatures may be sufficient to erase data. This state isdescribed as the superparamagnetic limit, which determines the maximumtheoretical storage density for a given magnetic media. This limit maybe raised by increasing the coercivity of the magnetic media or bylowering the temperature. Lowering the temperature may not always bepractical when designing hard disk drives for commercial and consumeruse. Raising the coercivity, on the other hand, may result in arequirement for write heads that incorporate higher-magnetic-momentmaterials, or techniques such as perpendicular recording (or both).

One additional solution has been proposed, which uses heat to lower theeffective coercivity of a localized region on the magnetic media surfaceand writes data within this heated region. The data state becomes“fixed” upon cooling the media to ambient temperatures. This techniqueis broadly referred to as “thermally assisted (magnetic) recording” (TARor TAMR), “energy assisted magnetic recording” (EAMR), or “heat-assistedmagnetic recording” (HAMR). The term “HAMR” is used herein to refer toall of TAR, TAMR, EAMR, and HAMR.

There is an ongoing need to improve the performance of write heads,including HAMR write heads.

SUMMARY

This summary represents non-limiting embodiments of the disclosure.

Disclosed herein are write heads with dual return poles for data storagedevices and data storage devices (e.g., hard disk drives) comprisingsuch write heads. A magnetic write head comprises a leading side, atrailing side, an air-bearing surface (ABS), a main pole disposedbetween the leading side and the trailing side and extending to the ABS,a first return pole disposed between the main pole and the leading side,and a second return pole disposed between the main pole and the trailingside.

In some embodiments, the main pole comprises a tapered portion at theABS, wherein the tapered portion comprises a trailing-side edge at anangle to the ABS, wherein the angle is less than 90 degrees. In somesuch embodiments, the trailing-side edge is a first trailing-side edgeand the angle is a first angle, and the tapered portion furthercomprises a second trailing-side edge recessed from the ABS and at asecond angle from the ABS, wherein the second angle is less than 90degrees. The first and second angles may be substantially equal, or thesecond angle may be less than the first angle. In some embodiments, thesecond angle is approximately zero.

In some embodiments in which the main pole comprises a tapered portion,the tapered portion further comprises a third trailing-side edge,wherein the third trailing-side edge is disposed between the firsttrailing-side edge and the second trailing-side edge, and wherein thethird trailing-side edge is substantially perpendicular to the ABS.

In some embodiments in which the main pole comprises a tapered portion,the tapered portion is a first tapered portion, and the second returnpole comprises a second tapered portion at the ABS and extending towardthe main pole.

In some embodiments, the second return pole comprises a tapered portionat the ABS and extending toward the main pole. In some such embodiments,the tapered portion comprises a main-pole-facing edge at an angle fromthe ABS, wherein the angle is greater than 90 degrees. In someembodiments, the tapered portion comprises a first main-pole-facing edgeand a second main-pole-facing edge, wherein each of the first and secondmain-pole-facing edges is substantially perpendicular to the ABS. Insome such embodiments, the tapered portion further comprises a thirdmain-pole-facing edge, wherein the third main-pole-facing edge issubstantially perpendicular to the ABS.

In some embodiments, a magnetic write head comprises an air-bearingsurface (ABS), a main pole extending to the ABS, a first return poleextending to the ABS and disposed between the main pole and a leadingside of the magnetic write head, and a second return pole disposedbetween the main pole and a trailing side of the magnetic write head,wherein the second return pole comprises a tapered portion adjacent tothe ABS, wherein the tapered portion extends in a direction toward themain pole. In some such embodiments, a distance between the main poleand the second return pole is between approximately 600 nm and 1000 nm.

In some embodiments, the tapered portion comprises a stacked structure.In some embodiments, the tapered portion comprises a wedge.

In some embodiments, the tapered portion is a first tapered portion, andthe main pole comprises a second tapered portion adjacent to the ABS,wherein the second tapered portion extends in a direction toward thefirst return pole. In some such embodiments, the first tapered portioncomprises a wedge or a stacked structure. In some embodiments, thesecond tapered portion comprises an edge facing the second return pole,wherein the edge is at an angle to the ABS, wherein the angle is lessthan 90 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages of the disclosure will be readilyapparent from the following description of certain embodiments taken inconjunction with the accompanying drawings in which:

FIG. 1 illustrates a hard disk drive into which the embodimentsdisclosed herein may be incorporated.

FIG. 2 is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 3A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 3B is a closer view of portions of the main pole and second returnpole.

FIG. 4A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 4B is a closer view of portions of the main pole and second returnpole.

FIG. 5A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 5B is a closer view of portions of the main pole and second returnpole.

FIG. 6A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 6B is a closer view of portions of the main pole and second returnpole.

FIG. 7A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 7B is a closer view of portions of the main pole and second returnpole.

FIG. 8A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 8B is a closer view of portions of the main pole and second returnpole.

FIG. 9A is a cross-sectional schematic of a portion of an exemplarymagnetic write head in accordance with some embodiments.

FIG. 9B is a closer view of portions of the main pole and second returnpole.

FIG. 10 is a plot comparing the perpendicular component of the magneticfield as a function of the write current for a write head with a singlereturn pole to that of a write head with two return poles as disclosedherein.

FIG. 11 is a plot comparing the down-track magnetic field as a functionof write current for a write head with a single return pole to that of awrite head with two return poles as disclosed herein.

FIG. 12 is a plot comparing the magnitude of the magnetic field as afunction of write current for a write head with a single return pole tothat of a write head with two return poles as disclosed herein.

FIG. 13 is a plot comparing the angle of the magnetic field as afunction of write current for a write head with a single return pole tothat of a write head with two return poles as disclosed herein.

FIG. 14 is a plot comparing the perpendicular component of the magneticfield as a function of down-track location for three write heads.

FIG. 15 is a two-dimensional plot of the perpendicular component of thewrite field generated by the write head corresponding to the dash-dotcurve of FIG. 14.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the disclosure. Itshould be understood, however, that the disclosure is not limited tospecific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thedisclosure. Furthermore, although embodiments of the disclosure mayachieve advantages over other possible solutions and/or over the priorart, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the disclosure. Thus, the followingaspects, features, embodiments and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s). Likewise, reference to“the disclosure” shall not be construed as a generalization of anyinventive subject matter disclosed herein and shall not be considered tobe an element or limitation of the appended claims except whereexplicitly recited in a claim or claims.

FIG. 1 is a top view of a head/disk assembly of a hard disk drive 10with the cover removed. The disk drive 10 includes a rigid base 12supporting a spindle 14 that supports at least one disk 16. The spindle14 is rotated by a spindle motor (not shown), which, in operation,rotates the at least one disk 16 in the direction shown by the curvedarrow 17. The hard disk drive 10 has at least one load beam assembly 20having an integrated lead suspension (ILS) or flexure 30 with an array32 of electrically conductive interconnect traces or lines. The at leastone load beam assembly 20 is attached to rigid arms 22 connected to anE-shaped support structure, sometimes called an E-block 24. The flexure30 is attached to an air-bearing (or, in the case that helium or anothergas is used instead of air inside the disk drive, a gas-bearing) slider28. A magnetic recording read/write head 29 is located at the end ortrailing edge of the slider 28. The flexure 30 enables the slider 28 to“pitch” and “roll” on an air (or gas) bearing generated by the rotatingdisk 16.

The disk drive 10 also includes a rotary actuator assembly 40rotationally mounted to the rigid base 12 at a pivot point 41. Theactuator assembly 40 may include a voice coil motor (VCM) actuator thatincludes a magnet assembly 42 fixed to the base 12 and a voice coil 43.When energized by control circuitry (not shown), the voice coil 43 movesand thereby rotates E-block 24 with attached arms 22 and the at leastone load beam assembly 20 to position the read/write head 29 over thedata tracks on the disk 16. The trace interconnect array 32 connects atone end to the read/write head 29 and at its other end to read/writecircuitry contained in an electrical module or chip 50, which, in theexemplary disk drive 10 of FIG. 1, is secured to a side of the E-block24. The chip 50 includes a read/write integrated circuit (R/W IC).

As the disk 16 rotates, the disk 16 drags air or another gas (e.g.,helium) under the slider 28 and along the air-bearing surface (ABS) ofthe slider 28 in a direction approximately parallel to the tangentialvelocity of the disk 16. As the air passes under the ABS, aircompression along the air flow path causes the air pressure between thedisk 16 and the ABS to increase, which creates a hydrodynamic liftingforce that counteracts the tendency of the at least one load beamassembly 20 to push the slider 28 toward the disk 16. The slider 28 thusflies above the disk 16 but in close proximity to the surface of thedisk 16.

The slider 28 supports the read/write head 29. As the disk 16 rotates inthe direction of the arrow 17, the movement of the actuator assembly 40allows the read/write head 29 on the slider 28 to access different datatracks on the disk 16. The slider 28 is typically formed of a compositematerial, such as a composite of alumina/titanium-carbide (Al₂O₃/TiC).FIG. 1 illustrates only one disk 16 surface with associated slider 28and read/write head 29, but there may be multiple disks 16 stacked on ahub that is rotated by a spindle motor, with a separate slider 28 andread/write head 29 associated with each surface of each disk 16.

For writing, the read/write head 29 may be a perpendicular recordinghead that includes a main pole and a return pole. The main pole andreturn pole are separated from each other by a write gap at the ABS andare connected to each other at a region distal from the ABS by a backgap closer or back via. One or more layers of conductive coils,encapsulated by insulating layers, are positioned between the main poleand the return pole. To write data to the disk 16, an electric currentflows through the conductive coils to induce a magnetic field across thewrite gap between the main pole and the return pole. By reversing thedirection of the current through the coil(s), the polarity of the datawritten to the magnetic media may be reversed.

In some embodiments, the read/write head 29 includes a HAMR-enabledwrite head. (As stated previously, the term “HAMR” as used herein refersto all variants of thermally-assisted recording, including TAR, TAMR,EAMR, and HAMR.) In HAMR, a magnetic recording material with highmagneto-crystalline anisotropy (K_(u)) is heated locally while theHAMR-enabled write head writes to lower the coercivity enough forwriting to occur, but the coercivity/anisotropy is high enough that therecorded bits are thermally stable at the ambient temperature of thedisk drive (i.e., the normal operating or “room” temperature ofapproximately 15-30 degrees Celsius). In some proposed HAMR systems, themagnetic recording material is heated to near or above its Curietemperature. The recorded data may then be read back at ambienttemperature by a conventional magnetoresistive read head. HAMR diskdrives have been proposed for both conventional continuous media,wherein the magnetic recording material is a continuous layer on thedisk, and for bit-patterned media (BPM), in which the magnetic recordingmaterial is patterned into discrete data islands or “bits.”

One type of HAMR-enabled write head uses a laser source and an opticalwaveguide coupled to a near-field transducer (NFT) for heating therecording material on the disk. Light from the laser source heats aportion of the magnetic recording medium (e.g., the disk 16) prior to awrite operation being performed. The NFT is typically located at the ABSof the slider that rides or “flies” above the disk surface. A NFT mayhave a generally triangular output end, such that an evanescent wavegenerated at a surface of the waveguide couples to surface plasmonsexcited on the surface of the NFT, and a strong optical near-field isgenerated at the apex of the triangular output end.

The light from the laser can be focused via a waveguide core layer andthe NFT on a precise location of the magnetic medium to reduce thecoercivity of that location of the magnetic medium prior to the mainwrite pole performing a write operation. This allows improved arealdensity to be achieved by allowing the laser to be focused precisely sothat the light can be directed at the desired location on the magneticrecording medium. A semiconductor laser with a wavelength of, forexample, 780 to 980 nm may be used as the HAMR light source. The lasermay be supported on the top of the slider 28, or it may be located onthe flexure 30 and coupled to the slider 28 by an optical channel.

In operation, after the voice coil 43 has positioned the read/write head29 over the data tracks on the disk 16, the read/write head 29 (e.g., aHAMR-enabled write head) may be used to write information to one or moretracks on the surface of the disk 16 and to read previously-recordedinformation from the tracks on the surface of the disk 16. The tracksmay comprise discrete data islands of magnetizable material (e.g.,bit-patterned media), or the disk 16 may have a conventional continuousmagnetic recording layer of magnetizable material. Processing circuitryin the hard drive 10 (e.g., on the chip 50) provides to the read/writehead 29 signals representing information to be written to the disk 16and receives from the read/write head 29 signals representinginformation read from the disk 16.

To read information from the disk 16, the read/write head 29 may includeat least one read sensor. The read sensor(s) in the read/write head 29may include, for example, one or more giant magnetoresistance (GMR)sensors, tunneling magnetoresistance (TMR) sensors, or another type ofmagnetoresistive sensor. When the slider 28 passes over a track on thedisk 16, the read/write head 29 detects changes in resistance due tomagnetic field variations recorded on the disk 16, which represent therecorded bits.

FIG. 2 is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100A in accordance with some embodiments. Themagnetic write head 100A is included in a slider 28, and may includelayers and/or components that are not illustrated in FIG. 2. Themagnetic write head 100A has a leading side 102, a trailing side 104,and an ABS 150. The leading side 102 is closer than the trailing side104 to the leading edge of the slider 28, and the trailing side 104 iscloser than the leading side 102 to the trailing edge of the slider 28.The leading side 102 passes over the region of the media to be writtenbefore the trailing side 104 passes over. In other words, referring toFIG. 1 and the arrow 17 showing the direction in which the disk 16rotates, the leading side 102 is closer than the trailing side 104 tothe pivot point 41.

The magnetic write head 100A includes a stitching layer 160 coupled to amain pole 130, which is configured to emit a recording magnetic fieldfor affecting the magnetic media. The main pole 130 serves as a firstelectrode and has a front portion at the ABS 150. The magnetic writehead 100A also includes a first return pole 110, which serves as asecond electrode and also has a front portion at the ABS 150. As shownin FIG. 2, the first return pole 110 is closer to the leading side 102than is the main pole 130. Similarly, the main pole 130 is closer to thetrailing side 104 than is the first return pole 110. The stitching layer160 is recessed from the ABS 150 by a distance 140.

The magnetic write head 100A, which may be a HAMR head, may also includea NFT and a waveguide, which may be positioned between the main pole 130and the first return pole 110. In embodiments in which the magneticwrite head 100A includes a NFT and waveguide, during operation,electromagnetic energy (e.g., light) from a laser source is introducedinto the waveguide and propagates along the length of the waveguide. Anevanescent wave is generated at the surface of the waveguide proximatethe ABS 150. The evanescent wave polarizes in a direction along theplane of the ABS 150, coupling to a surface plasmon excited on thesurface of the NFT output tip. The surface plasmon causes charges tomove in a down-track direction and concentrate in the space at the ABS150 between the NFT output tip and the end of the main pole 130,subsequently generating a localized electrical field that is known as anoptical near-field spot. The electric field heats a portion of the hardrecording layer of the magnetic media, thereby lowering its coercivityin the specific portion or “bit” so that the magnetic field from themain pole 130 can alter its magnetization. The main pole 130 thenapplies a magnetic field and affects the magnetization of the portion ofthe magnetic media at the optical near-field spot.

As shown in FIG. 2, at the ABS 150, the main pole 130 and the firstreturn pole 110 are separated by a distance 170A. A first flux closurepath for the main pole 130 is provided by the first return pole 110,which may be, relatively speaking, a considerable distance from the mainpole 130, particularly if a waveguide and NFT are situated between themain pole 130 and the first return pole 110 as described above. Largerdistances 170A can result in slower saturation (and, therefore, slowerswitching speed) relative to smaller distances 170A. Therefore, toimprove switching speed and performance of the magnetic write head 100A,it is desirable to improve the flux closure.

One way to improve the switching speed and performance of the magneticwrite head 100A is to reduce the distance 170A between the main pole 130and the first return pole 110. But, when the magnetic write head 100Aincludes HAMR optics, doing so may reduce the optical efficiency, whichcan have a negative impact on the performance of the magnetic write head100A. Furthermore, reducing the distance 170A between the main pole 130and the first return pole 110 can undesirably increase the down-trackcomponent of the write field while decreasing the perpendicularcomponent. Therefore, there is a need for solutions that improveswitching speed (i.e., the time needed to switch the magneticpolarization of the poles of the magnetic write head) without incurringsubstantial optical losses and magnetic field degradations (e.g.,decreases in the perpendicular component and/or increases in thedown-track component).

To improve the flux closure, the exemplary embodiment of FIG. 2 providesa second return pole 120 between the main pole 130 and the trailing side104. The main pole 130 and first and second return poles 110, 120 areboth constructed of a magnetic material that produces a high saturationflux density, such as, for example, NiFe, CoFeNi, or CoFe. In theembodiment of FIG. 2, the second return pole 120 has a similar shape tothe first return pole 110, except that it extends toward the main pole130 at the ABS 150. The portion of the second return pole 120 thatextends toward the main pole 130 has a height 122 extending in thedirection perpendicular to the ABS 150. At the ABS 150, the secondreturn pole 120 ends a distance 170B from the main pole 130. Thedistance 170B may be, for example, between approximately 600 nm andapproximately 1000 nm. The distances 140, 170B and the height 122 of thesecond return pole 120 may be optimized to improve the flux closure.

FIG. 3A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100B in accordance with some embodiments, and FIG.3B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100B. Like the magnetic write head100A of FIG. 2, the magnetic write head 100B of FIG. 3A includes a mainpole 130, a stitch layer 160, a first return pole 110, and a secondreturn pole 120. The stitch layer 160, first return pole 110, and secondreturn pole 120 shown in FIG. 3A were described in the discussion ofFIG. 2, and that description is not repeated here.

In the embodiment shown in FIGS. 3A and 3B, the main pole 130 includes atapered portion 132 at the ABS 150 (i.e., the tapered portion 132extends to the ABS 150). As shown, the tapered portion 132 becomesprogressively smaller toward the ABS 150. The tapered portion 132 has atrailing-side edge 133 that is at an angle 134 to the ABS 150. In theembodiment shown in FIGS. 3A and 3B, the angle 134 is less than 90degrees. At the ABS 150, the tapered portion 132 extends for a distance136 in the down-track direction (i.e., in the y-direction using the axesshown in FIGS. 3A and 3B). In the embodiment illustrated in FIGS. 3A and3B, the tapered portion 132 extends in a direction toward the firstreturn pole 110. In other embodiments, the tapered portion 132 mayextend in a direction toward the second return pole 120.

At the ABS 150, the main pole 130 and the second return pole 120 areseparated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm. The main pole130 has an edge 131 that is substantially perpendicular to the ABS 150.The second return pole 120 has a main-pole-facing edge 125, which, asshown in FIG. 3B, is substantially perpendicular to the ABS 150. Themain-pole-facing edge 125 and a projection of the edge 131 to the ABS150 are separated by a distance 142 at the ABS 150. The height 122(which is also the length of the main-pole-facing edge 125 in theembodiment of FIGS. 3A and 3B), the distances 136, 142, and 170, theangle 134, and the length of the edge 133 (and other characteristics,including other dimensions, angles, materials, etc.) may be selected oroptimized (e.g., jointly) to provide a desired level of improvement inthe flux closure.

FIG. 4A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100C in accordance with some embodiments, and FIG.4B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100C. Like the magnetic write heads100A and 100B of FIGS. 2A-3A, the magnetic write head 100C of FIGS. 4Aand 4B includes a main pole 130, a stitch layer 160, a first return pole110, and a second return pole 120. In the embodiment of FIGS. 4A and 4B,both the main pole 130 and the second return pole 120 include taperedportions 132, 124 at the ABS 150. The main pole 130 and its taperedportion 132 were described in the discussion of FIGS. 3A and 3B, andthat description is not repeated here.

In the exemplary magnetic write head 100C, the second return pole 120also includes a tapered portion 124. The tapered portion 124 has amain-pole-facing edge 125 that is at an angle 126 to the ABS 150. In theembodiment illustrated in FIGS. 4A and 4B, the angle 126 is greater than90 degrees, thus making the tapered portion 124 a wedge. The angles 126and 134 may be in some relation (e.g., they may be supplementaryangles), or they may have no relationship to each other. Themain-pole-facing edge 125 and a projection of the edge 131 to the ABS150 are separated by a distance 142 at the ABS 150.

The tapered portion 124 of the second return pole 120 extends toward themain pole 130 and has a maximum height 122, as measured from the ABS150. As will be appreciated by skilled artisans, the length of themain-pole-facing edge 125 may be derived from the height 122 and theangle 126 (i.e., as the maximum height 122 divided by the sine of thesupplementary angle to the angle 126 (i.e., 180 degrees minus the angle126)).

At the ABS 150, the main pole 130 and the second return pole 120 areseparated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm. The maximumheight 122, the distance 136, the distance 170, the angles 126, 134, andthe lengths of the edges 125, 133 (as well as any other characteristics,e.g., dimensions, materials, etc.) may be selected or optimized (e.g.,jointly) to provide a desired level of improvement in the flux closure.

FIG. 5A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100D in accordance with some embodiments, and FIG.5B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100D. Like the magnetic write heads100A, 100B, and 100C of FIGS. 2A-4B, the magnetic write head 100D ofFIGS. 5A and 5B includes a main pole 130, a stitch layer 160, a firstreturn pole 110, and a second return pole 120. The stitch layer 160 andfirst return pole 110 were described in the discussion of FIG. 2, andthat description is not repeated here. The main pole 130 with a taperedportion 132 was described in the discussion of FIGS. 3A and 3B, and thatdescription is not repeated here.

The exemplary magnetic write head 100D also includes a second returnpole 120 with a tapered portion 124. In the exemplary embodiment ofFIGS. 5A and 5B, the tapered portion 124 is a stacked structure. Astacked structure is any union of geometric shapes assembled to form thetapered portion 124. For example, a stacked structure may be made fromthe union of two quadrilaterals (e.g., the rectangles illustrated inFIGS. 5A and 5B, a trapezoid and a rectangle, etc.). The stackedstructure of FIGS. 5A and 5B comprises two quadrilateral shapes 128A and128B. The quadrilateral shape 128A includes the main-pole-facing edge125A, which has a length 122A. The quadrilateral shape 128B includes themain-pole-facing edge 125B, which has a length equal to the maximumheight 122B of the tapered portion 124 minus the length 122A.

The tapered portion 124 of the second return pole 120 extends toward themain pole 130 and has a maximum height 122B, as measured from the ABS150. The main-pole-facing edge 125A and a projection of the main poleedge 131 to the ABS 150 are separated by a distance 142A at the ABS 150.The main-pole-facing edge 125B is recessed from the ABS 150. Itsdistance from the projection of the edge 131 is the distance 142B, asshown in FIGS. 5A and 5B.

At the ABS 150, the main pole 130 and the second return pole 120 areseparated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm. The maximumheight 122B, the length 122A, the distances 136, 142A, 142B, and 170,the angle 134, and the lengths of the edges 125A, 125B, 133 (as well asany other characteristics, e.g., dimensions, materials, etc.) may beselected or optimized (e.g., jointly) to provide a desired level ofimprovement in the flux closure.

FIG. 6A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100E in accordance with some embodiments, and FIG.6B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100E. Like the magnetic write heads100A, 100B, 100C, and 100D of FIGS. 2A-5B, the magnetic write head 100Eof FIGS. 6A and 6B includes a main pole 130, a stitch layer 160, a firstreturn pole 110, and a second return pole 120. The stitch layer 160 andfirst return pole 110 were described in the discussion of FIG. 2, andthat description is not repeated here. The main pole 130 with a taperedportion 132 was described in the discussion of FIGS. 3A and 3B, and thatdescription is not repeated here.

The exemplary magnetic write head 100E also includes a second returnpole 120 with a tapered portion 124. The tapered portion 124 has amaximum height 122C, as measured from the ABS 150. In the exemplaryembodiment of FIGS. 6A and 6B, the tapered portion 124 is a stackedstructure comprising three quadrilateral shapes 128A, 128B, 128C. In theexemplary embodiment of FIGS. 6A and 6B, the three quadrilateral shapes128A, 128B, and 128C are rectangles, but it is to be understood thatother shapes may also or alternatively be used. The quadrilateral shape128A includes the main-pole-facing edge 125A, which has a length 122A.The quadrilateral shape 128B includes the main-pole-facing edge 125B,which has length equal to the height 122B minus the length 122A. Thequadrilateral shape 128C includes the main-pole-facing edge 125C, whichhas length equal to the maximum height 122C minus the height 122B.

The tapered portion 124 of the second return pole 120 extends toward themain pole 130. The main-pole-facing edge 125A and a projection of themain pole edge 131 to the ABS 150 are separated by a distance 142A atthe ABS 150. The main-pole-facing edge 125B is recessed from the ABS150. Its distance from the projection of the edge 131 is the distance142B, as shown in FIGS. 5A and 5B. Similarly, the main-pole-facing edge125C is also recessed from the ABS 150. Its distance from the projectionof the edge 131 is the distance 142C, as shown in FIGS. 6A and 6B.

At the ABS 150, the main pole 130 and the second return pole 120 areseparated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm. The heights122B, 122C, the length 122A, the distances 136, 142A, 142B, 142C, 170,and 136, the angle 134, and the lengths of the edges 125A, 125B, 133 (aswell as any other characteristics, e.g., dimensions, materials, etc.)may be selected or optimized (e.g., jointly) to provide a desired levelof improvement in the flux closure.

It is to be understood that the stacked structures illustrated in FIGS.5A through 6B are merely examples of stacked structures. They are notmeant to limit the characteristics of stacked structures that may formthe tapered portion 124 of the second return pole. As explained above,the shapes making up a stacked structure need not be rectangular inshape. Any suitable shapes (e.g., triangles, quadrilaterals, etc.) maybe used. The stacked structure may include additional or alternativecomponents (e.g., more than two or three shapes), which may have anysuitable size and shape. Moreover, each shape making up the stackedstructure may be a combination of shapes (e.g., a trapezoid stacked on arectangle).

FIGS. 3A through 6B illustrate one embodiment of a tapered main pole130. FIGS. 7A through 9B illustrate several other embodiments.

FIG. 7A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100F in accordance with some embodiments, and FIG.7B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100F. Like the magnetic write heads100A, 100B, 100C, 100D, 100E of FIGS. 2A-6B, the magnetic write head100F of FIGS. 7A and 7B includes a main pole 130, a stitch layer 160, afirst return pole 110, and a second return pole 120. The stitch layer160 and first return pole 110 were described in the discussion of FIG.2, and that description is not repeated here. The second return pole 120with a tapered portion 124 as shown in FIGS. 7A and 7B was described inthe discussion of FIGS. 4A and 4B, and that description is not repeatedhere. It is to be understood that although FIGS. 7A and 7B show thetapered portion 124 from FIGS. 4A and 4B, the tapered portion 124 mayhave any suitable shape and characteristics. Other exemplary embodimentsof the tapered portion were discussed in the descriptions of FIGS.5A-6B.

The main pole 130 includes a tapered portion 132 at the ABS 150 (i.e.,the tapered portion 132 extends to the ABS 150). At the ABS 150, thetapered portion 132 extends for a distance 136A in the down-trackdirection (i.e., in the y-direction using the axes shown in FIGS. 7A and7B).

The tapered portion 132 has a trailing-side edge 133 that is at an angle134 to the ABS 150. In the embodiment shown in FIGS. 7A and 7B, theangle 134 is less than 90 degrees. The tapered portion 132 also has anedge 137 that extends toward the second return pole 120 and issubstantially parallel to the ABS 150. The edge 137 has a length 136B.

At the ABS 150, the main pole 130 and the second return pole 120 areseparated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm. The height 122,the distances 136A, 136B, 142, and 170, the angle 134, and the length ofthe edge 133 (and other characteristics, including other dimensions,angles, materials, etc.) may be selected or optimized (e.g., jointly) toprovide a desired level of improvement in the flux closure.

FIG. 8A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100G in accordance with some embodiments, and FIG.8B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100G. Like the magnetic write heads100A, 100B, 100C, 100D, 100E, and 100F of FIGS. 2A-7B, the magneticwrite head 100G of FIGS. 8A and 8B includes a main pole 130, a stitchlayer 160, a first return pole 110, and a second return pole 120. Thestitch layer 160 and first return pole 110 were described in thediscussion of FIG. 2, and that description is not repeated here. Thesecond return pole 120 with a tapered portion 124 as shown in FIGS. 8Aand 8B was described in the discussion of FIGS. 4A and 4B, and thatdescription is not repeated here. It is to be understood that althoughFIGS. 8A and 8B show the tapered portion 124 from FIGS. 4A and 4B, thetapered portion 124 may have any suitable shape and characteristics.Other exemplary embodiments of the tapered portion were discussed in thedescriptions of FIGS. 5A-6B.

The main pole 130 includes a tapered portion 132 at the ABS 150 (i.e.,the tapered portion 132 extends to the ABS 150). At the ABS 150, thetapered portion 132 extends for a distance 136A in the down-trackdirection (i.e., in the y-direction using the axes shown in FIGS. 8A and8B). At the ABS 150, the main pole 130 and the second return pole 120are separated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm.

The tapered portion 132 has a first trailing-side edge 133A that is atan angle 134A to the ABS 150. In the embodiment shown in FIGS. 8A and8B, the angle 134A is less than 90 degrees. The tapered portion 132 alsohas a second trailing-side edge 133B that is recessed from and at anangle 134B to the ABS 150. In the embodiment of FIGS. 8A and 8B, theangle 134B is less than the angle 134A. In other embodiments, the angles134A, 134B are substantially equal, or the angle 134B is greater thanthe angle 134A. The angle 134B may be approximately zero, thereby makingthe trailing-side edge 133B substantially parallel to (but recessedfrom) the ABS 150. The first and second trailing-side edges 133A, 133Bintersect at a point that is a distance 136B from a projection towardthe ABS 150 of the main pole edge 131. As will be appreciated by skilledartisans, the lengths of the trailing-side edges 133A, 133B may bederived using trigonometry and, for example, the distances 136B, 142,170 and the angles 134A, 134B. For example, the length of thetrailing-side edge 133B is the distance 136B divided by the cosine ofthe angle 134B, and the length of the trailing-side edge 133A is thedistance 170, minus the distances 136B, 142, divided by the cosine ofthe angle 134A.

The height 122, the distances 136A, 136B, 142, and 170, the angles 134A,134B, and the lengths of the edges 133A, 133B (and othercharacteristics, including other dimensions, angles, materials, etc.)may be selected or optimized (e.g., jointly) to provide a desired levelof improvement in the flux closure.

FIG. 9A is a cross-sectional schematic of a portion of an exemplarymagnetic write head 100H in accordance with some embodiments, and FIG.9B is a closer view of portions of the main pole 130 and second returnpole 120 of the magnetic write head 100H. Like the magnetic write heads100A, 100B, 100C, 100D, 100E, 100F, and 100G of FIGS. 2A-8B, themagnetic write head 100H of FIGS. 9A and 9B includes a main pole 130, astitch layer 160, a first return pole 110, and a second return pole 120.The stitch layer 160 and first return pole 110 were described in thediscussion of FIG. 2, and that description is not repeated here. Thesecond return pole 120 with a tapered portion 124 as shown in FIGS. 9Aand 9B was described in the discussion of FIGS. 4A and 4B, and thatdescription is not repeated here. It is to be understood that althoughFIGS. 9A and 9B show the tapered portion 124 from FIGS. 4A and 4B, thetapered portion 124 may have any suitable shape and characteristics.Other exemplary embodiments of the tapered portion were discussed in thedescriptions of FIGS. 5A-6B.

The main pole 130 includes a tapered portion 132 at the ABS 150 (i.e.,the tapered portion 132 extends to the ABS 150). At the ABS 150, thetapered portion 132 extends for a distance 136A in the down-trackdirection (i.e., in the y-direction using the axes shown in FIGS. 9A and9B). At the ABS 150, the main pole 130 and the second return pole 120are separated by a distance 170. The distance 170 may be, for example,between approximately 600 nm and approximately 1000 nm.

The tapered portion 132 has a first trailing-side edge 133A that is atan angle 134A to the ABS 150. In the embodiment shown in FIGS. 9A and9B, the angle 134A is less than 90 degrees. The tapered portion 132 alsohas a second trailing-side edge 133B that is recessed from andsubstantially perpendicular to the ABS 150. In other embodiments, thesecond trailing-side edge 133B is not perpendicular to the ABS 150. Thesecond trailing-side edge 133B has a length 135 and is a distance 136Bfrom a projection toward the ABS 150 of the main pole edge 131. Thetapered portion 132 also has a third trailing-side edge 133C that isrecessed from and at an angle 134B to the ABS 150. In the embodiment ofFIGS. 9A and 9B, the angle 134B is less than the angle 134A. In otherembodiments, the angles 134A, 134B are substantially equal, or the angle134B is greater than the angle 134A. The angle 134B may be approximatelyzero, making the third trailing-side edge 133C substantially parallel to(but recessed from) the ABS 150.

As will be appreciated by skilled artisans, the lengths of thetrailing-side edges 133A, 133C may be derived using trigonometry and,for example, the distances 136B, 142, 170 and the angles 134A, 134B.

The height 122, the distances 136A, 136B, 142, and 170, the angles 134A,134B, the length 135, and the lengths of the edges 133A, 133C (and othercharacteristics, including other dimensions, angles, materials, etc.)may be selected or optimized (e.g., jointly) to provide a desired levelof improvement in the flux closure.

FIG. 10 is a plot comparing the perpendicular component of the magneticfield, in Oersted, as a function of the write current, in mA, for awrite head with a single return pole to that of a write head with tworeturn poles as disclosed herein. As FIG. 10 illustrates, the additionof a second return pole results in a substantial increase in theperpendicular component of the magnetic field for a selected writecurrent. Stated another way, the addition of a second return poleenables the write head to provide a target perpendicular field using alower write current.

FIG. 11 is a plot comparing the down-track magnetic field, in Oersted,as a function of write current, in mA, for a write head with a singlereturn pole to that of a write head with two return poles as disclosedherein. As FIG. 11 illustrates, the addition of a second return poleresults in a slightly higher magnetic field in the down-track directionfor a selected write current up to about 70 mA. But, as FIG. 10 shows,the increase in down-track component of the magnetic field is more thanoffset by the gains in the perpendicular component. As a result, overallperformance of the write head is improved with the use of a secondreturn pole as described herein.

FIG. 12 is a plot comparing the magnitude of the magnetic field, inOersted, as a function of write current, in mA, for a write head with asingle return pole to that of a write head with two return poles asdisclosed herein. As FIG. 12 illustrates, the addition of a secondreturn pole results in a higher magnetic field magnitude for a selectedwrite current up to about 80 mA. Stated another way, the addition of asecond return pole enables the write head to provide a target magneticfield magnitude using a lower write current.

FIG. 13 is a plot comparing the angle of the magnetic field as afunction of write current for a write head with a single return pole tothat of a write head with two return poles as disclosed herein. As shownin FIG. 13, the angle of the field is largely unaffected by the additionof the second return pole.

FIG. 14 is a plot comparing the perpendicular component of the magneticfield as a function of down-track location for exemplary three writeheads. The solid curve corresponds to a write head has only a singlereturn pole. The other two curves correspond to write heads that havetwo return poles as disclosed herein. The dashed curve illustrates theperpendicular component of a write head with a non-tapered second returnpole, and the dash-dot curve illustrates the perpendicular component ofa write head with a tapered second return pole. As FIG. 14 shows, theaddition of a second return pole provides a stronger perpendicularcomponent at all locations of interest in the down-track direction. Asthe dash-dot curve shows, tapering the second return pole reduces thedistance between the main pole and the second return pole, which causesthe peak in the perpendicular component to occur at a down-tracklocation of just under 0.6 microns. In contrast, the peaks for thesingle-return-pole write head and the dual-return-pole write headwithout a tapered second return pole are near 1 micron.

FIG. 15 is a two-dimensional plot of the perpendicular component of thewrite field generated by the write head corresponding to the dash-dotcurve of FIG. 14. As shown, the maximum amplitude of the perpendicularcomponent of the write field in the down-track direction occurs at justunder 0.6 microns at the center (0.00 cross-track).

It will be appreciated that there are nearly limitless combinations ofmain poles 130 and second return poles 120 that may take advantage ofthe disclosures herein. The illustrative embodiments shown herein aresimply examples of different main pole 130 and second return pole 120combinations. Other combinations are possible. As just one example, thetapered main poles 130 illustrated in FIGS. 7A-9B may be used incombination with any of the tapered second return poles 120 illustratedin FIGS. 5A-6B. Likewise, a particular implementation may include atapered main pole 130 and a non-tapered second return pole 120, or anon-tapered main pole 130 and a tapered second return pole 120.Similarly, an implementation may include a non-tapered main pole 130 anda non-tapered second return pole 120.

Moreover, although the disclosure herein discusses tapering of thesecond return pole 120, the first return pole 110 may also oralternatively be tapered. Tapered return poles 110 for use in HAMR writeheads are disclosed in co-pending U.S. patent application Ser. No.16/022,273, filed Jun. 28, 2018, and entitled “MAGNETIC WRITE HEAD WITHA TAPERED RETURN POLE.” The entirety of the contents of U.S. patentapplication Ser. No. 16/022,273 are hereby incorporated by reference forall purposes.

In the foregoing description and in the accompanying drawings, specificterminology has been set forth to provide a thorough understanding ofthe disclosed embodiments. In some instances, the terminology ordrawings may imply specific details that are not required to practicethe invention.

It is to be understood that although the disclosure is presented hereinin the context of HAMR, the concepts and exemplary embodiments are notlimited to HAMR implementations. The techniques and embodimentsdisclosed herein may be used in other types of write heads and othertypes of data storage devices.

To avoid obscuring the present disclosure unnecessarily, well-knowncomponents (e.g., of a magnetic write head) are shown in block diagramform and/or are not discussed in detail or, in some cases, at all.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation, including meanings implied fromthe specification and drawings and meanings understood by those skilledin the art and/or as defined in dictionaries, treatises, etc. As setforth explicitly herein, some terms may not comport with their ordinaryor customary meanings.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” do not exclude plural referents unless otherwisespecified. The word “or” is to be interpreted as inclusive unlessotherwise specified. Thus, the phrase “A or B” is to be interpreted asmeaning all of the following: “both A and B,” “A but not B,” and “B butnot A.” Any use of “and/or” herein does not mean that the word “or”alone connotes exclusivity.

As used in the specification and the appended claims, phrases of theform “at least one of A, B, and C,” “at least one of A, B, or C,” “oneor more of A, B, or C,” and “one or more of A, B, and C” areinterchangeable, and each encompasses all of the following meanings: “Aonly,” “B only,” “C only,” “A and B but not C,” “A and C but not B,” “Band C but not A,” and “all of A, B, and C.”

To the extent that the terms “include(s),” “having,” “has,” “with,” andvariants thereof are used in the detailed description or the claims,such terms are intended to be inclusive in a manner similar to the term“comprising,” i.e., meaning “including but not limited to.” The terms“exemplary” and “embodiment” are used to express examples, notpreferences or requirements.

The terms “over,” “under,” “between,” and “on” are used herein refer toa relative position of one feature with respect to other features. Forexample, one feature disposed “over” or “under” another feature may bedirectly in contact with the other feature or may have interveningmaterial. Moreover, one feature disposed “between” two features may bedirectly in contact with the two features or may have one or moreintervening features or materials. In contrast, a first feature “on” asecond feature is in contact with that second feature.

The drawings are not necessarily to scale, and the dimensions, shapes,and sizes of the features may differ substantially from how they aredepicted in the drawings.

Although specific embodiments have been disclosed, it will be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the disclosure. Forexample, features or aspects of any of the embodiments may be applied,at least where practicable, in combination with any other of theembodiments or in place of counterpart features or aspects thereof.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

What is claimed is:
 1. A heat-assisted magnetic recording (HAMR) writehead, comprising: a leading side; a trailing side; an air-bearingsurface (ABS); a main pole disposed between the leading side and thetrailing side and extending to the ABS; a first return pole disposedbetween the main pole and the leading side and extending to the ABS; awaveguide disposed between the first return pole and the main pole andextending to the ABS; a near-field transducer disposed between thewaveguide and the main pole and extending to the ABS; and a secondreturn pole disposed between the main pole and the trailing side andextending to the ABS.
 2. The HAMR write head recited in claim 1, whereinthe main pole comprises a tapered portion at the ABS, wherein thetapered portion comprises a trailing-side edge at an angle to the ABS,wherein the angle is less than 90 degrees.
 3. The HAMR write headrecited in claim 2, wherein the trailing-side edge is a firsttrailing-side edge and the angle is a first angle, and wherein thetapered portion further comprises a second trailing-side edge recessedfrom the ABS and at a second angle from the ABS, wherein the secondangle is less than 90 degrees.
 4. The HAMR write head recited in claim3, wherein the first and second angles are substantially equal.
 5. TheHAMR write head recited in claim 3, wherein the second angle is lessthan the first angle.
 6. The HAMR write head recited in claim 5, whereinthe second angle is approximately zero.
 7. The HAMR write head recitedin claim 3, wherein the tapered portion further comprises a thirdtrailing-side edge, wherein the third trailing-side edge is disposedbetween the first trailing-side edge and the second trailing-side edge,and wherein the third trailing-side edge is substantially perpendicularto the ABS.
 8. The HAMR write head recited in claim 2, wherein thetapered portion is a first tapered portion, and wherein the secondreturn pole comprises a second tapered portion at the ABS and extendingtoward the main pole.
 9. The HAMR write head recited in claim 1, whereinthe second return pole comprises a tapered portion at the ABS andextending toward the main pole.
 10. The HAMR write head recited in claim9, wherein the tapered portion comprises a main-pole-facing edge at anangle from the ABS, wherein the angle is greater than 90 degrees. 11.The HAMR write head recited in claim 9, wherein the tapered portioncomprises a first main-pole-facing edge and a second main-pole-facingedge, wherein each of the first and second main-pole-facing edges issubstantially perpendicular to the ABS.
 12. The HAMR write head recitedin claim 11, wherein the tapered portion further comprises a thirdmain-pole-facing edge, wherein the third main-pole-facing edge issubstantially perpendicular to the ABS.
 13. A magnetic storage systemcomprising the HAMR write head recited in claim
 1. 14. A heat-assistedmagnetic recording (HAMR) write head, comprising: an air-bearing surface(ABS); a main pole extending to the ABS; a first return pole extendingto the ABS and disposed, at the ABS, between the main pole and a leadingside of the magnetic write head; a waveguide extending to the ABS anddisposed, at the ABS, between the first return pole and the main pole; anear-field transducer extending to the ABS and disposed, at the ABS,between the waveguide and the main pole; and a second return poledisposed between the main pole and a trailing side of the magnetic writehead, wherein the second return pole comprises a tapered portionadjacent to the ABS, wherein the tapered portion extends in a directiontoward the main pole.
 15. The HAMR write head recited in claim 14,wherein a distance between the main pole and the second return pole isbetween approximately 600 nm and 1000 nm.
 16. The HAMR write headrecited in claim 14, wherein the tapered portion comprises a stackedstructure.
 17. The HAMR write head recited in claim 14, wherein thetapered portion comprises a wedge.
 18. The HAMR write head recited inclaim 14, wherein the tapered portion is a first tapered portion, andwherein the main pole comprises a second tapered portion adjacent to theABS, wherein the second tapered portion extends in a direction towardthe first return pole.
 19. The HAMR write head recited in claim 18,wherein the first tapered portion comprises a wedge or a stackedstructure.
 20. The HAMR write head recited in claim 18, wherein thesecond tapered portion comprises an edge facing the second return pole,wherein the edge is at an angle to the ABS, wherein the angle is lessthan 90 degrees.